Aspirin is a very dangerous medication for cats and dogs. It is not effective for pain or inflammation in cats (it is only used for blood clot prevention in cats). The proper dose for a cat is small and only once or twice weekly as this drug stays in their system a long time. Giving small doses more often than twice weekly, or giving a single larger dose can be fatal.
Aspirin is frequently recommended (on the internet) for dogs with arthritis – do an internet search on ‘dogs and aspirin’ and all kinds of sites come up. You may notice that most of these sites sell aspirin for dogs… Aspirin is a very poor pain medication for dogs. The effects are very mild for pain relief, and the side-effects are bad. The worst part is that the effective dose for pain relief (what little pain relief aspirin provides) and the dose where side effects occur are pretty much the same. This means you do not need to overdose your dog with aspirin – just giving it a few times at the correct dose can cause major problems.
What kind of problems are commonly caused by giving aspirin to dogs? There are several. Nausea, decreased appetite, GI bleeding, and stomach ulcers are the most common side effects seen. Aspirin also affects blood clotting. Dogs have died from a nosebleed after taking too much aspirin. A third potential side effect of aspirin is a major problem for some dogs. Aspirin reacts badly with steroids and with all NSAIDs (Non Steroidal Anti Inflammatory Drugs). These are most of our strong medications for pain. If you give your dog aspirin, and then he or she needs stronger medication for pain, or for a medical condition like a back injury, we cannot safely give any of these other drugs for 7 to 10 days. This really limits how we can treat your dog as well as how well we can control your dog’s pain…
So, please don’t give your dog or cat any doses of aspirin uness it has been prescribed by your veterinarian, and then follow the directions precisely. Stop giving aspirin to your dog at the first sign of nausea, any decreased appetite, vomiting, dark or tarry stools, etc. Also, if your dog is scheduled to have any surgery (no matter how minor), or a teeth cleaning procedure, stop giving aspirin 2 weeks before hand!